The above-described porous aluminum sintered compact is used for, for example, electrodes and current collectors in a variety of batteries, heat exchanger components, silencing components, filters, impact-absorbing components, and the like.
In the related art, the above-described porous aluminum sintered compact is produced using, for example, the methods disclosed by Patent Documents 1 to 5.
In Patent Document 1, a mixture is formed by mixing aluminum powder, paraffin wax particles, and a binder, and the mixture is shaped into a sheet shape. This mixture is naturally dried. Next, the mixture is immersed in an organic solvent so as to remove the wax particles, subsequently, drying, defatting, and sintering are carried out; and thereby, a porous aluminum sintered compact is produced.
In addition, in Patent Documents 2 to 4, aluminum powder, sintering aid powder containing titanium, a binder, a plasticizer, and an organic solvent are mixed together so as to form a viscous composition, the viscous composition is shaped and foamed. Then, the viscous composition is heated and sintered in a non-oxidizing atmosphere; and thereby, a porous aluminum sintered compact is produced.
Furthermore, in Patent Document 5, base powder consisting of aluminum, Al alloy powder used to form bridging portions which contains a eutectic element, and the like are mixed together and the mixture is heated and sintered in a hydrogen atmosphere or a mixed atmosphere of hydrogen and nitrogen; and thereby, a porous aluminum sintered compact is produced. Meanwhile, this porous aluminum sintered compact has a structure in which the particles of the base powder consisting of aluminum are connected together through bridging portions having a hypereutectic structure.
Meanwhile, in the porous aluminum sintered compact and the method for producing the porous aluminum sintered compact described in Patent Document 1, there has been a problem in that it is difficult to obtain a porous aluminum sintered compact having high porosity. Furthermore, in the case in which the aluminum base materials are sintered together, the bonding between the aluminum base materials is hindered by oxide films formed on the surfaces of the aluminum base materials and there has been a problem in that it is not possible to obtain a porous aluminum sintered compact having sufficient strength.
In addition, in the porous aluminum sintered compact and the method for producing the porous aluminum sintered compact described in Patent Documents 2 to 4, there has been a problem in that, since the viscous composition is shaped and foamed, it is not possible to efficiently produce a porous aluminum sintered compact. Furthermore, there has been another problem in that, since the viscous composition contains a large amount of a binder, a long period of time is required for a binder removal treatment, the shrinkage ratio of the compact becomes large during sintering, and it is not possible to produce a porous aluminum sintered compact with excellent dimensional accuracy.
Furthermore, in the porous aluminum sintered compact and the method for producing the porous aluminum sintered compact described in Patent Document 5, there is provided a structure in which the particles of the base powder consisting of aluminum are bonded together through the bridging portions having a hypereutectic structure. In this structure, Al alloy powder having a eutectic composition and a low melting point is melted so as to generate a liquid phase and the liquid phase is solidified among the base powder particles; and thereby, the bridging portions are formed. Therefore, it has been difficult to obtain a porous aluminum sintered compact having high porosity.